The Associated Press is reporting a large explosion in the Iranian city of Qazvin. The AP says that many casualties are expected. The city is located just to the west of the capital Tehran.

Here’s what we know so far:

1. Qazvin May Have a Secret Nuclear Weapons Plant

(Google Maps)

It had been reported in 2009 that Qazvin was the site of secret uranium enrichment plant. It was reported by Fars News Agency in Iran on May 5 that an inspection team from the International Atomic Energy Agency arrived in the country to inspect a uranium mine in Central Iran.

2. Reports From Iran Indicate Up to 50 People Have Been Killed

Sajjad Eslamian, a reporter with the Iranian news agency has tweeted that the explosion happened in a cellar and that up to 50 people have been killed or injured.

3. The Cause of the Explosion is Unknown

Smoke around Qazvin and reports of people evacuated, but I'm not seeing news of an explosion, Mehr news says the fire was caused by welding.

It’s unknown what the cause of the explosion was. Thomas Erdbrink with The New York Times reports that local news reports are saying an oil storage is burning. He added that people are being evacuated from the area but that he hasn’t seen reports of an explosion. The RT reports that firefighters have been battling a blaze at an oil depot in the region for hours.